1. Field of the Invention
The present invention relates to a cylinder injection type fuel injection valve to be attached to a cylinder head in order to directly inject fuel into a combustion chamber in an internal combustion engine.
2. Discussion of Background
A conventional cylinder injection type fuel injection valve has a general structure in a combination of an injection valve body with a needle valve and a solenoid for operating the needle valve. The solenoid comprises a housing, a core, a coil assembly and O-rings for sealing fuel which are provided between the coil assembly and the housing and between the coil and coil assembly so as to prevent fuel from leaking.
FIG. 24 is a cross-sectional view partly omitted showing an example of a conventional cylinder injection type fuel injection valve wherein numeral 31 designates a coil, numeral 32 designates a mold portion in a coil assembly, numeral 33 designates a core, numeral 34 designates a housing, numeral 35 designates an armature, numeral 36 designates a valve unit, and numerals 37, 38 designate O-rings.
In such cylinder injection type fuel injection valve attached to the cylinder head of a fuel engine so that fuel is directly injected into a fuel chamber, a quicker response is required. Accordingly, in order to obtain a high response characteristic, the coil is so made as to have a low resistance of 5.OMEGA. or less, or to increase a voltage to be applied, or to employ both the techniques.
In employment of the above-mentioned techniques, however, when an intense current of, for example, 3A or higher is passed, there causes a fault in a driving circuit or insulation breakdown. Further, in a case that an intense current is continuously passed for a certain time or more, the coil 31 (FIG. 24) generates heat, and the mold portion 32 of the coil assembly is softened or molten, whereby a gap is produced at a portion other than the sealing portion in the coil assembly thereby resulting leakage of fuel, or a surface of elements at a portion A or a portion B is deformed thereby causing leakage of fuel.